My daughter has the same problem of being scared to like my BF, out of fear that her daddy will get angry with her.
My BF has been awesome about it! And he doesn,t have any kids of his own either.

It broke my heart when she explained it to me. I had worked so hard to ensure that she didn't feel uncomfortable with his new girlfriend and he would badmouth me and my bf and she was just so confused. He has finally come around and talked to her and ensured her that he would love her regardless. She drew an adorable picture of our house, with me, her brother, her and my bf. That's a big step because all previous pictures only included her daddy and now she is comfortable enough to include my bf.